Cannot Burn M Discs

[Rte80west]

I also posted this under ARABESK, just not sure it will be seen there so posted here as well.

OK, using a Karat with two Blu Ray burners. On these burners is the M Disc logo - obviously an indication it should burn M discs right? M Discs are BD-R format. ~ 198 minute storyboard, burns fine to a regular Memorex Blu Ray BD-R dvd. I put in the Blu ray M disc dvd and it indicates disc cant burn, likely isnt blank. I tried several new discs so I dont think thats it. This DOES burn M Discs correct? THe LG burners indicate it does. Is a firmware update needed or drivers? Frustrated... any advice very much appreciated